Bacterial biofilm mechanical properties persist upon antibiotic treatment and survive cell death

Abstract

Bacteria living on surfaces form heterogeneous three-dimensional consortia known as biofilms, where they exhibit many specific properties one of which is an increased tolerance to antibiotics. Biofilms are maintained by a polymeric network and display physical properties similar to that of complex fluids. In this work, we address the question of the impact of antibiotic treatment on the physical properties of biofilms based on recently developed tools enabling the in situ mapping of biofilm local mechanical properties at the micron scale. This approach takes into account the material heterogeneity and reveals the spatial distribution of all the small changes that may occur in the structure. With an Escherichia coli biofilm, we demonstrate using in situ fluorescent labeling that the two antibiotics ofloxacin and ticarcillin-targeting DNA replication and membrane assembly, respectively-induced no detectable alteration of the biofilm mechanical properties while they killed the vast majority of the cells. In parallel, we show that a proteolytic enzyme that cleaves extracellular proteins into short peptides, but does not alter bacterial viability in the biofilm, clearly affects the mechanical properties of the biofilm structure, inducing a significant increase of the material compliance. We conclude that conventional biofilm 4

Disruption and eradication ofP. aeruginosabiofilms using nitric oxide-releasing chitosan oligosaccharides

“…In addition to preventing the removal of pathogens, thickened CF mucus restricts bacterial motility and promotes P. aeruginosa biofilm formation (Matsui et al 2006). While biofilms are traditionally defined as cooperative communities of bacteria within a protective matrix (Mah & O'Toole 2001), they also constitute viscoelastic materials with well-defined physical and mechanical properties (Lieleg et al 2011, Zrelli et al 2013). Strategies for treating P. aeruginosa biofilms and infections in the CF airways to date have focused on reducing bacterial viability through antibiotic treatment, specifically through the use of inhalable tobramycin.…”

Direct Comparison of Physical Properties of Bacillus subtilis NCIB 3610 and B-1 Biofilms

“…While Bacillus subtilis biofilms are formed on solid nutrient surfaces or at liquid-air interfaces (10,11), other bacteria can produce biofilms on surfaces under water-saturated conditions (in liquid) (12). Due to their high mechanical stability (13,14) and their resistance to antibiotic or chemical treatment (15)(16)(17)(18), such biofilms present significant problems in both industry and health care (19)(20)(21)(22). Although the compositions of many biofilm matrices are known, the biomolecular reason for the outstanding resistance of bacterial biofilms is not well understood.…”

Biomechanical Analysis of Infectious Biofilms

“…Cellular growth under continuous flow resulted in stiffer biofilms for the same species, which may be a physiological response to sustained mechanical stress, although the failure strain did not significantly vary [4]. Antibiotics of sufficient concentration to destroy the majority of cells had no significant effect on the stiffness of the E. coli matrix, but it was drastically weakened by the protease trypsin, suggesting a dominant role for proteins in the matrix mechanics of this species [106]. By contrast, a broad range of chemical agents had no significant affect of the mechanics of P. aeruginosa biofilms, but could influence the rate of recovery from non-linear strains [55], possibly due to chemical modification of inter-molecular associations between matrix components.…”

“…For one particle, the motions of micron-scale particles undergoing passive Brownian motion are converted to G * (ω) or J * (ω) using thermodynamic relations [31,61,62], or they are actively driven via external forces and the moduli extracted directly [37,106]. These particles are either added, or are endogenous such as the cells themselves [76].…”

“…Other shear-based removal devices include microbubble jets for oral hygiene [46], and automated wipers [33] and wall-scraping 'pigs' [91] in industry. An integrated removal strategy first exposes biofilms to sublethal concentrations of antibiotics or other chemical agents, which can lead to reduced stiffness and enhanced removal, although crosslinkers and multivalent ions can increase stiffness [55,106]. In addition, modifying the topographic, chemical or elastic properties of abiotic surfaces can reduce cell attachment or promote weak bonding that can be more easily removed [13,24,33,35,49].…”